<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>简单计算</title>
</head>
<body>
  <script>
    let num1 =+prompt('请输入数字一')
    let num2 =+prompt('请输入数二')
    let a =prompt('+-*/')
    switch (a){
      case '+':a
      alert(num1+num2)
      break;
                case '-':a
      alert(num1-num2)
      break;
                case '*':a
      alert(num1*num2)
      break;
                case '/':a
      alert(num1/num2)
      break;
      default:
        alert('没有找到')
        break;
    }
  </script>
</body>
</html>